Some smaller firms estimate that as many as a quarter to a third of their staff could be at risk if Government does not give Sizewell C the go-ahead.
The warning about the impact of losing another major nuclear scheme after Hitachi abandoned the Wylfa project in Anglesey comes from a 100-strong group of leading firms in the industry.
These include Atkins, Arup, Balfour Beatty, BAM, Laing O’Rourke, Mace, William Hare, and Wood.
It comes as the Government is looking at options for how to financially support the EDF developed project.
EDF has called on the government to launch a new regulated asset base – RAB – funding model to help the project get built.
This would see British households pay through their electricity bills while the plants are still being constructed. But this would expose taxpayers to any cost over-runs and delays during construction.
Loss of this experienced skills base now would be a major blow to the civil nuclear industry, which employs around 60,000 people.
These jobs are vital if the UK is to maintain the capability to construct new nuclear projects, including emerging technologies such as Small Modular Reactors (SMRs), Advanced Modular Reactors (AMRs) and energy from hydrogen.
Cameron Gilmour, spokesperson for the Sizewell C Consortium, said: “For the first time in a generation the UK has developed a world-class nuclear construction and engineering supply chain.
“Without Sizewell C, we will not sustain it – and thousands of jobs could be lost as a result.
“This is not a viable option for Britain. Government needs to get on with giving the green light to Sizewell C.”
Sizewell C would provide a multi-billion pounds economic stimulus for Britain, creating 25,000 job opportunities and 1500 apprenticeships across the East of England and the wider UK. British-based firms will deliver 70% of contracts by value during the construction phase.
The project will be a replica of Hinkley Point C. By dovetailing the two projects key parts of the Hinkley supply chain can capitalise on efficiencies, productivity gains and lower supplier costs.